1. Field of the Invention
This invention relates to a mounting apparatus for mounting a chip component, such as a semiconductor chip, onto the mounting portion of a lead frame, and a method for controlling the load on the chip component.
2. Description of the Related Art
FIG. 7 shows a conventional mounting apparatus, for example, a die bonding apparatus. An arm 61 has a table 61a, on which a motor 62 is mounted. The motor 62 has an axis 62a of rotation, to which a screw 63 is directly secured. A collet head 64 is mounted on the screw 63. Thus, the motor 62 can move the collet head 64 in the vertical direction.
The collet head 64 has a main body 64a, in which a collet shaft 65 is inserted such that it is movable in the vertical direction. A stopper 66a is provided on an upper portion of the collet shaft 65, and a collet 73 for holding a semiconductor chip (hereinafter called a "die") 72 with the use of a vacuum chuck is provided on a lower portion of the same. Further, an engagement member 66b is provided on a lower portion of the shaft 65, and a spring 69 is interposed between the main body 64a of the collet head 64 and the engagement member 66b.
A gap sensor 70 is provided on an upper portion of the collet head 64 when the die 72 is out of contact with a lead frame 71, the collet shaft 65 is urged by the spring 69 downward as indicated by arrow-A. Accordingly, the stopper 66a contacts the gap sensor 70. At the time of bonding, the motor 62 is driven to lower the collet head 64, thereby bringing the die 72 into contact with the lead frame 71 coated with a paste 74. Further lowering the collet head 64 will cause a deviation in position between the collet head 64 and the collet shaft 65, since the collet shaft 65 is kept stopped during the further lowering operation. This causes a gap between the gap sensor 70 and the stopper 66a. As this time, the gap sensor 70 senses that the die 72 has contacted the lead frame 71. Rotating the motor 62 for a predetermined amount causes the die 72 to press the lead frame 71.
The above-described conventional die bonding apparatus determines whether or not the die 72 has contacted the lead frame 71, on the basis of whether or not the gap sensor 70 contacts the stopper 66a. In this case, however, unless the spring 69 is contracted to some extent after the die 72 has contacted the lead frame 71, the stopper 66a is not separated from the gap sensor 70. As a result, the initial impact load applied to the die 72 is not small. Further, it is difficult to finely control the load applied thereto by motor rotation control. Accordingly, it is liable that the die 72 is cracked, degrading its quality.